Pressure Washing in Dublin: Which Surfaces Take It, and Which Don’t

Dublin has a wider spread of paving than anywhere else in the country. A Georgian granite step in Portobello, a 1970s concrete drive in Artane, cobblelock laid across half of Swords and Tallaght in the 1990s, porcelain in a recently redone back garden in Rathmines. They all go grey and green at roughly the same rate. They do not all want the same treatment.

This is the question worth answering before anyone turns a machine on, because pressure washing in Dublin goes wrong in exactly one way: the right tool used on the wrong surface.

What takes pressure well

Dense, hard, unsealed surfaces. Concrete slabs, poured concrete, tarmac, block paving and cobblelock, brick paviours, granite, limestone, porcelain. On these the soiling is ingrained rather than sitting on a coating, the material itself is not going anywhere, and the result is immediate rather than gradual.

That immediacy is the real argument for it. On hard paving you are not waiting for anything to weather off — the surface comes back during the visit, and you can see the line between done and not done as the work moves across it.

What does not

Timber decking, painted concrete, soft sandstone and composite boards. Each fails differently and none of them fail gracefully.

Timber raises its grain and furs up, and once the fibres have been lifted they stay lifted. Painted concrete is a coating on a surface, so what comes off is the coating. Soft sandstone pits, and the pitting holds dirt better than the original face did, so it looks worse sooner the next time. Composite boards scar in a way that catches the light at an angle and never settles back.

These are softwash surfaces. The growth is treated rather than blasted, and the wall or board is left intact. The general reasoning behind that split is set out in soft washing vs pressure washing.

The awkward middle: old concrete

The surface that causes the most argument is tired concrete — a 1960s or 1970s drive that has been rained on for fifty years and has lost its surface laitance in patches.

It is hard enough to take pressure in principle. The difficulty is that it is no longer uniform, so it does not respond uniformly, and a pass that cleans one section can start opening up the aggregate in another. The answer is not a single setting for the whole drive. It is testing a small area first, setting pressure and nozzle to what the worst of the surface will take rather than the best, and accepting that a fifty-year-old drive comes back clean rather than new.

Why the nozzle matters more than the machine

People generally ask about pressure in bar or PSI. That number is the least useful part of the answer.

What actually reaches the paving is decided by the nozzle angle, the distance held, and the speed of the pass. A narrow nozzle held close concentrates everything the machine has onto a few square centimetres; the same machine with a wider fan held further back cleans without cutting. This is why two people with identical equipment get very different results, and why a machine hired for a weekend so often leaves stripes that are still visible a year later.

Stripes are the giveaway. They are not dirt left behind — they are the clean sections cut slightly deeper than the rest.

What Dublin adds on top

Three things, depending on where in the county you are.

Traffic film, everywhere within the M50 and along the main routes out of it: brake dust and soot lay a grey layer over paving that reads as “faded” rather than “dirty”. Salt, on the coastal side — Malahide, Howth, Sutton, Clontarf, Dún Laoghaire, Killiney — which keeps surfaces damp longer and encourages growth. And tannin, under the mature trees of Rathgar, Ranelagh, Terenure and Clontarf, which stains rather than soils and behaves differently from either.

None of these change which surfaces take pressure. They change how much there is to remove and how quickly it returns.

The part that gets skipped

Jointing. Block paving and slab joints are filled with kiln-dried sand, and washing moves some of it. If it is not replaced, the blocks lose their interlock, weeds get in faster than before, and the drive starts moving under vehicle weight at the edges.

A drive cleaned and not re-sanded looks better for about a season and is then in worse condition than when it started. It is the single most common thing missing from a cheap job, and it is not visible on the day.

How to tell what you have

Most people do not know whether their patio is limestone or concrete, and there is no reason they should. Two quick checks get you most of the way: tap it, because concrete sounds dull and stone rings slightly; and look at a cut edge or a step nosing, where concrete shows aggregate and stone shows grain.

If that does not settle it, a photograph does. We would far rather look at a picture and tell you it wants a softwash than turn up with the wrong plan. The full county coverage and what we take on is on the pressure washing in Dublin page.

Common questions

Related services

• Pressure washing in Dublin
• Softwashing for render and walls
• Roof cleaning in Dublin